US2413529A - Tractor crane - Google Patents

Description

Dec. 31, 1946. R. c. SWANEY 2,413,529

' TRACTOR CRANE Filed Nov. 6, 1944 4 Sheets-Sheet 1 R. C. SWAN EY- TRACTOR CRANE Dec. 31, 1946.

4 Sheets-Sheet 2 Filed Nov. 6, 1944 zmw wt? R. C. SWANEY TRACTOR CRANE Filed NW. 6, 1944 Dec. 31; 1946.

4 Sheets-Sheet 3 Dec. 31, 1946; R.. c. SWANEY 2,413,529

' a I TRACTOR CRANE Filed Nov. 6, 1944 4 Sheets-Sheet 4 4 means forming part of the Patented Dec. 31, '1946 TRACTOR CRANE Robert Casper. Swaney, Newton, Mass., assignor of one-fourth to Laura B. Swaney, one-fourth to Laura B. Swaney, as guardian of C. Barnett Swaney, one-fourth to Laura B. Swaney, as

' guardian of Mary Jane Swaney, all of Newton,

Mass.

Application November 6, 1944, Serial No. 562,138

28 Claims. (Cl. 212-8) The invention here involved is concerned with crane equipment for tractors, and tractors provided with cranes, for the purpose of picking up heavy' loads, transporting them from place to place, and depositing them at desired spots. One object of the invention is to furnish a tractor crane combination which is rugged, powerful and easily operated. Another and particular object is to provide a crane or derrick as a structural combination capable of being applied and connected to existing tractors with a minimum of reconstruction or structural modification of the tractor. Another object is to provide a crane structure and a combination of such a structure with a tractor which is of the utmost simplicity but is capable of performing all of the duties required of such a crane apparatus, in which the forces and reactions are taken up and absorbed by the crane structure. itself and which affords flexibility permitting thetracks or tractive belts of the machine to accommodate themselves to uneven conditions of the ground.

The invention consists in the combinations, constructions and parts hereinafter described with reference to one illustrative embodiment, and in all equivalents thereof in which the same fundamental members are embodied.

In the -drawings- 2 represents the hood in which the engine of the tractor is contained, ll represents the drivers seat, I 2 represent a bracket (the supporting frame of the power control unit) secured to the rear end of the tractor frame and supporting winch drums l3 and I4 by which the load line and topping line are controlled, and I represents a part of the driving mechanism for the drums.

. The bracket l2 also supports guide pulleys l6, l6

Fig. 1 is a side elevation of a tractor crane embodying the invention;

Fig. 2 is a rear elevation of said tractor crane;

Fig. 3 is a plan view of thesame;

Fig. 4 is a detail sectional view of cable guiding crane combination taken on line 4-4 of Fig. 3;

Fig. 5 is a detail section taken on line 5-5 of Fig. 4;

Fig. 6 is a cross section of part of one of the traction units of the machine taken on line 6-6 of Fig. 1;

Fig. 7 is a detail sectional view of one of the support brackets for the parts of the crane, being a modification of the corresponding bracket shown in Fig. 6;

Fig. 8 is a view similar to Fig. 2 showing an alternative design of mast and boom.

Like reference characters designate the same parts wherever they occur in all the figures.

The tractor shown in these drawings is a standard model of one of the well known commercial tractors equipped with hoisting means of the type, commonly known as a two-drum power control unit, and control means by which the drums are driven for hoisting loads and their rotation is retarded when the loads are lowered. Here In and I1, I! around which these lines are led. Further details of drum driving mechanism, the brakes by which they are retarded when loads are being lowered, and the control levers are not here shown, as all these parts are standard equipment. It is suflicient to say that in this equipment of such control units only two hand levers are neededto afiord complete control of the drums in taking up and paying out the lines.

The traction units are standard, each comprising two channel bars l8 having bearings I9 in which is mounted the shaft 20 of a driving sprocket 2|, and bearings 22 in which the shaft of an idle pulley 23 rotates. The tractive belt 24 passes around the sprocket and pulley. Supporting rolls 25 are journaled in bearings 26 secured to the under edges of the channel bars 18 and rest on sectional tracks 2'! carried by the tread pieces 28 of which the tractive belt is composed. Shaft 20, driven by the engine, rotates in the bearings l9, and the entire tractor unit is capable of swinging about that shaft in passing over uneven ground, springs being interposed between forward parts of the traction unit frame and the tractor chassis to support the weight of this part of the tractor body yieldingly., Although this is all standard construction, a general description of it is given here to make plain that the tractor units may swing up and down independently of one another about the power shaft 20 when passing over bumps and obstacles on the ground.

The crane equipment comprises a mast 29, a, boom 30 and a part 3| which I calla counter arm and which serves as a brace or tie member for the head of the mast. The mast isa strong and rigid structure made of steel channel bars and plates secured together by welding or other suitable means to form a beam 32 in its upper portion and three feet 33, 34 and 35, respectively, which lie in a plane at an angle to the beam 32. The feet are provided with eyes at their extremities, in axial alinement, which are coupled by pins 36, 31and 38 with lugs 39; 40 and 4|, respectively, on a support bracket 42, which is secured to the outer channel bar l8 of one of the traction units. There are two middle lugs 40 on the support bracket between which the eye of the middle foot of the mast is received. Other lugs 43 and 3d are provided on the support bracket. adjacent to each end thereof and outside of the lugs 39 and M. These outer lugs embrace the terminal eyes of the boom 3@ and assist in supporting the pivot pins 36 and 38 by which the outer feet of the mast and the terminal eyes of the boom are coupled to the support bracket.

The beam portion 32 of the mast extends on an upward slant across substantially the full width of the tractor and its head carries a lug 55 to which the upper end of the counter arm 3! is connected by a pivot pin 36. The lower end of the counter arm is coupled to the middle lugs of a support bracket ll which is a duplicate of the bracket 42 and is secured to the outer channel bar of the other traction unit. The coupling includes a link Q8 connected at one end by a pivot 39 to the counter arm 38 and at its other end to the bracket lugs by a pivot which is substantially at right angies to the pivot t6. These pivots are close together and make in efiect a universal joint, permitting a relative angular movement in all directions between the counter arm and the traction unit.

An important advantage results from the arrangement of the mast and the disposition of its head and point of connection with the counter arm in substantially or nearly vertical alinement with the location at which the counter arm is connected with the traction unit. This is the elimination of lateral stress by the parts of the.

crane on the traction units. I he truth of this statement will be apparent from the following analysis. When the boom is in an inclined or horizontal position, the weight of the boom and any suspended load, and the pull of the topping line, create a resultant force which is applied to the traction unit along the length of the boom. The horizontal component of this force is exerted inwardly toward the center line of the tractor.

- But the tension in the topping line is balanced by compressive stress in the mast which exerts force on the traction unit with a horizontal component equal and opposite to that applied by the boom. Thus the only unbalanced forceapplied to the traction unit acts vertically downward, when the machine is on level ground. The turning moment of the mast and crane assemblage due to the load is balanced by the tensile stress in the counter arm 3i, which applies force vertically upward to the opposite traction unit. For the foregoing reasons, I claim as an important factor of the invention the disposition of the mast head and counter arm substantially vertically over the lower point of connection of the counter arm. However, the invention includes other possible arrangements which sacrifice this advantage in greater or less measure, for such other arrangements are operative even though less satisfactory.

The boom is an A frame made of steel H bars, the upper ends of which are secured together, by welding or otherwise, and the lower or foot ends are spread apart and provided with eyes which receive the pivot pins 36 and 38 respectively in the spaces between the pairs of end lugs 43, 44. A plate is set into notches in the adjoining outer ends of the H bars and welded in place. The ends of this plate project and provide a lug 50 at one side of the boom and a lug at the other side. Cap plates 50! are welded on the outer ends of these bars, covering the channels between their flanges.

A bridle 52, which is a rigid bar or tube, is connected at one end to the lug 50 by a pivot 53, and it carries at its opposite end a cage 54 in which pulley sheaves 55 are mounted, such cage and sheaves constituting a pulley block. Lug 5i contains a number of holes into any of which a hook or bail may be placed for supporting the upper block 56 of the load fall, or otherwise supporting a load. Lugs or webs 57 are secured to the upper end of the mast head in parallel planes, supporting a pivot 58 on which sheaves 59 are mounted, and embracing the sheaves and serving as separators between adjacent sheaves. Said lugs and sheaves constitute a second pulley block.

A load line 60, anchored to one of the blocks of the load fall passes around sheaves in the upper and lower blocks 56 and BI and from the upper block to and under a guide sheave 62 mounted on the mast, thence around a guide pulley 63 (which is coupled with the mast in a manner later described), through a fair lead tube 64 rearwardly, thence over a guide pulley 65 on a post 66 which rises from the bracket 12 of the hoisting apparatus, and thence under one of the pulleys I1 and over one of the pulleys Hi to the hoisting drum 13. The guide pulley 62 for this line is located on the mast as near as feasible to the boom in order that the stress applied to the line 60 will have the least possible .tendency to elevate the boom.

The boom is swung around its pivot axis in handling loads by means of a topping line 61 which is anchored to the mast at 68, passes around the pulleys 55 and 59 in two or more stretches, thence around a guide pulley 69 on the mast, through the fair lead tube 64, over a guide beside the pulley 65, and to the drum H around the other set of pulleys I! and IS in a course substantially parallel to that of the load line.

By making the lugs 50 and 5| of a single integral piece of metal passing through the end of the boom and secured to it, the strongest possible structure for the raising of loads is furnished. It transmits stress directly from the load fall to the boom topping rig to the limit of its tensile strength, and is not liable to failure through a defective weld.

The post 66 is connected to bracket [2 by a pivot "HI- so that it can swing in a' substantially vertical plane forward and aft. It is connected with the fair lead tube. by a knuckle consisting of a yoke H on the fair lead tube embracing a pulley guide 12 on the post and connected with the latter by the same pivot 13 on which the guide pulley and the pulley beside it, over which the topping line passes, are mounted. Yoke H has a tubular stem 14 fitted rotatably in the fair lead tube and the pulley guide 12 has a stem I5 fitted rotatably in the upper end of post 66. These parts provide a universal coupling permitting relative angular movement between the post and fair lead tube about three axes substane tially at right angles to each other; and the forward and of the fair lead tube is connected to the mast by a coupling 16 constructed to permit angular movement about an' axis extending lengthwise of the mast and another axis substantially perpendicular both to the mast and to the fair lead tube. The pulleys 63 and 69 are supported by the fair lead tube at the end thereof next to the mast and are located at respectively opposite sides of the axis of the tube. They are here shown as supported by pivots 1! (one of which is tubular to permit passage of the line through it, as shown by Fig. 5) in a. frame secured to the tube, but this detail is not an essential feature. They could be mounted in a rigid frame, or otherwise mounted in fixed position, inasmuch as the leads-for both lines are lengthwise of the mast. However, the swivel arrangement permits either line to be led at various inclinations to the length of the mast if desired. With the use of the guide sheave 52, or an equivalent, the two lines 60 and 61 lead from the pulleys 63 and 69 in directions opposite to one another and substantially in alinement. Thus, when they jointly support a load, the stresses in them due to the load are balanced.

The members 64 and 66 act as struts which absorb th strain of the cables and relieve the frame of the tractor and traction units from racking stresses. If the cables were led directly from the mast\to the drums and no compression member were provided to absorb their pull they would apply a powerful side stress on the mast and a lifting stress on the rear end of the tractor, which would seriously hamper. the free movement of the traction unit to which the foot of the mast is connected. But by providing rigid members between the take up drums and the points at which the "cables leave the mast, the racking stresses due to the cables are absorbed and neutralized; and the articulation between the rigid members whereby they cause the cables to travel in an angular path enables these members to maintain a substantially constant length of cable between the drums and mast however the latter'may be inclined forward or aft due to movement of its supporting traction unit in passing over rough ground and obstacles. 1

A spring 88 is interposed between the boom and bridle to bear on abutments thereon near the hinge connection 53. This spring supports the .as is indicated by broken lines in Fig. 2. Then vertical when the tractor is on level ground; but

this is not essential. The rigid triangle or truss feature is important, however, and is obtainable with a bridle either longer or shorter than that here shown.

By virtue of the articulations through which the counter arm is coupled with the crane mast and the traction unit of the tractor, and those of the fair lead tube 64 and post 66, the full flexibility of the tractor .is preserved while the crane itself is rigid. Thus either traction unit may be raised above or lowered below the other in passing over bumps and irregularities of the ground without applying racking stress to either the tractor frame orgto the crane. If, for instance, the traction unitto which the feet of the mast and boom are pivoted swings upward or downward about its pivotal connection with the frame, the crane is tilted forward or aft, but the couplings at top and bottom of the counter arm 3| permit such movements without imparting appreciable bending stresses to the counter arm or weight of the bridle and pulley block 54 -55 and holds them away from the boom at a nearly constant angle with the boom when the topping line is slack, so that theblock will not be set to bobbing up and down when thetension in the topping line is suddenly changed due to conditions which frequently occur in handling loads and when the crane is moving. Other springs 89, of helical form, are mounted on the sides of the mast at the angle between the upright foot portion and the inclined beam portion thereof. They bear against brackets 90 on the mast and are supported by bars which project from the respective brackets into the coils of the respective springs. They are located in the paths of movement of the two arms of the boom and are en-- gaged and compressed by the latter when the boom is in and near the upright position shown by broken lines in Fig. 2. Their main purpose and function is to displace the boom from an upright position when the topping line is slackened to one that is so far inclined that "gravity becomes effective to lower it further. The boom can be placed in a, position where its center of gravity is vertically above the pivot'axis, or even inboard from thefvertical if the tractor rests on ground which raises the side to which the boom is pivoted higher than the other side,

' and infsuch cases gravity alone is insufficient to lower the boom and draw out the topping line when the line"is slackened. The springs afford means for insuring that the boom will be lowered in such circumstances.

The cage 54 on the bridle includes a transverse member or wall 9! (Fig. 3),which abuts against the pulley supporting lugs 51 of the mast head when the pulleys are brought block to block.

. purpose.

to the other parts of the structure, and the fair lead tube 64 and post 66. accommodate themselves to all such movements and retain the various guide pulleys at unvarying distances from each other at all times in position to absorb the stresses of the cables, as described, and in correct planes to guide the hoisting lines properly. The forces and reactions incident to raising and lowering loads except those incident to the articulated struts are borne by the crane structure itself and supported by the traction units at a low level near the ground. They are not transmitted to the body of the tractor.

It is not essential that the boom of the crane be pivoted directly to the frame of the traction unit, for it may be mounted directly on the mast and connected thereto by a. pivot at any desired location. Fig. 8 shows a modification in which a boom 30a is connected by pivots N10 to the mast on an axis near the vertex of the angle between the upright and inclined portions of the mast. This boom, like the boom 30, is an A frame and has legs which straddle the mast and are connected to the latter by two alined pivots. Springs 89a analogous to the springs 89 are supported by brackets 90a, secured to the side members of the mast in position to be engaged and compressed by the legs of the boom when the latter is substantially vertical, and to thrust the boom away when the topping line is slackened. In all other respects this crane combination is identical with that previously described and is mounted on the tractor and controlled by a twodrum power control unit and cables in the same way. Representation of the power control unit in Fig. 2 has been omitted from Fig. 8 for sim-, plicity. In both form's of crane the boom is sup-.

ported by one of the traction units exclusively and is arranged to swing about an axis extending lengthwise of the unit.

The ways in which the two lines 60 and 61 can be used conjointly to raise and lower loads will be obvious. It should be noted also that in some situations either line may be used alone for that Thus, the boom may be held at a desired inclination, without change of inclination,

this crane can be mounted on commercial tractors. Referring to Fig. 6, it will be seen that the support bracket 42 is provided on its inner side with two parallel keysways 9'2 and 93 spaced and dimensioned to receive the upper and lower flanges 0f the outer channel bar l8 of one traction unit, and that a bolt 94 passes through a hole in the support bracket into a tapped hole in an anchor bar 95, which is welded to the web of the channel bar between its flanges. There may be two such bolts located at the ends of the support bracket, as shown in Fig, 1, or any other number as desired. The flanges of the channel bar and the shoulders constituted by the upper walls of the keyways 92 and 93 support the weight of the crane, and the bolts 94 merely tie the bracket to the channel bar; the holes in the brackets through which the bolts pass being large enough to relieve the bolts of any shearing or bending stress.

The bracket 41 is secured to the other traction unit in the same way, and applies both the upward and downward stresses, transmitted through the counter arm 3|, to the correspond ing channel bar through its engagement with the flanges of the channel bar.

No change other than applying the anchor bars to the channel bars of the traction units is required to mount the crane on any commercial tractor which has traction unit frames of this design; and such attachments can be made in any shop t ere fusion welding equipment is available.

Fig. 7 illustrates a variation in design of support bracket applicable to tractors of which the outer longitudinal frame members are of box form in section. In this design of tractor the beam lBa, corresponding tothe channel bar l8 of Fig. 6, carries a plate 96 welded to its flanges and overlying the space between them. The bracket 91, which corresponds to the brackets 42 and 41, has a lip or shoulder 98 on the face opposite to that from which the lugs project,

which is placed so as to overlap the upper edge of the plate 96, and the bracket is made fast by a suitable number of bolts 99 threaded into tapped holes in the plate 96. All that is needed to apply the crane to tractors of the last described type is to drill and tap a 'sufiicient number of holes in the plates 96 of the two traction units to receive the connecting bolts.

Inasmuch as th brackets of both sides of. th tractor are alike, the crane can be mounted for operation at either the right or left side of the tractor, and can be easily shifted over from one side to the other, as occasion may demand. When the crane must be used in situations which prevent it from being turned around. this capability of shifting the crane from one side to the other is of great advantage.

What I claim and desire to secure by Letters Patent is:

1. A tractor crane comprising the combination with a tractor having traction units connected with the tractor to swing about a horizontal axis, of a mast and boom supported by a frame member of one of the traction units exclusively, with the boom pivoted to swing laterally with respect to the tractor, a connector between the head of the mast and the frame of the traction unit at the opposite side of the tractor from the beforementioned unit, hoisting means mounted on the tractor, and cables leading from said hoisting means to the mast and boom for raising and lowering loads and for swinging the boom.

2. A tractor crane comprising the combination with a tractor, of a mast mounted on one of the traction units of the tractor exclusively and rising therefrom and having an upper portion extending across the tractor to a point substantially vertically over the outer side of the other traction unit, a rigid connector in articulatedcom' nection at its lower end with said other traction unit exclusively and at its upper end with the mast at a point substantially vertically over its connection with the traction unit, a boom supported exclusively by the first named traction unit with capability for swinging movement between different angles with the vertical, hoisting means mounted on the tractor, and cables leading from said hoisting means to the mast and boom for raising and lowering loads and for swinging the boom.

3. A tractor crane comprising the combination with a tractor having traction units at its opposite sides, of a mast and boom supported exclusively by a frame member of one of the traction units with the boom pivoted to swing between different angles with the vertical, a connector between the head of the mast and the frame of the other traction unit, hoisting means mounted on the tractor, cables leading from said hoisting means to the mast and boom for raising and lowering loads and for swinging the boom, and guide means for the cables between the hoisting means and the mast arranged to lead the cables in angular paths and to balance the stresses in the cables.

f. The combination with a tractor having traction units at opposite sides, of support brackets connected respectively to outer frame members of the respective traction units, a mast supported entirely by the bracket of one of said units, a boom connected to swing about an axis extending lengthwise of the traction unit, a rigid counter arm connected to the bracket of the other of said units by pivot means having two axes transverse to one another, and pivotally connected to the mast, a load supporting means suspended from the boom, hoisting mechanism mounted on the tractor body, and a topping line running from said hoisting mechanism and so connected with the boom and mast as to control the raising and lowering of the boom about its pivotal connection with the first named bracket.

5. A tractor crane comprising the combination with a tractor having traction units at opposite sides, of a mast supported entirely on one of said traction units, a member supported entirely on the other traction unit and connected to the mast for bracing it, a boom pivoted to one of the traction units to swing about an axis extending longitudinally of the unit, means for applying force between the mast and boom for swinging above the latter traction unit for bracing the mast, a boom supported from the same traction unit to which the foot end of the mast is con- ,nected, pivotally mounted to swing in a plane transverse to the length of the tractor, a rigid bridle connected at one end to the outer part of the boom and having a pulley block at its other end, a pulley block-mounted rigidly on the head of the mast, a topping-line passing around sheaves of said pulley blocks for swinging the boom, and a load fall suspended from the boom; the mast, boom and bridle being arranged to constitute a rigid triangle when the blocks'on the bridle and mast are brought together.

7. A tractor crane comprising the combination with a tractor having traction units at opposite sides, of a mast formed with a bend between its head and foot ends, its foot end'being mounted on one of the traction units exclusively so that the part of the mast above the bend overlies the tractor, a member connected to the head of the mast and to the other traction unit exclusively at points in substantially vertical alinement for bracing the mast, a boom supported by the same traction unit to which the foot end of the mast is connected, in pivotal relation to the mast so as to swing in a' plane transverse to the length of the tractor, means including a topping line interconnected with the mast and boom at points distant from said pivotal support, for swinging the boom up and down about its pivotal support, and a spring carried by the mast in position to be engaged and. compressed by the boom when the latter is raised, whereby to impart force tending to lower the boom.

8. A tractor crane comprising the combination with a tractor having traction units at opposite sides, of a mast formed with a bend between its head and foot ends, its foot end being mounted on one of the traction units exclusively so that the part of the mast above the bend overlies the tractor, a member connected to the head of the mast and to the other traction unit exclusively for bracing the mast, a boom pivoted to the same traction unit to which the foot end of the mast is connected, arranged to swing in a plane transverse to the length of the tractor, between a substantially upright position and a lowered position, hoisting means coupled with the boom and mast controlling the swinging movement of=the boom, and a spring mounted on the mast in position to be engaged by the boom when the latter approaches itsupright position for displacing the boom from the upright position when the force of the hoisting means is relaxed.

9. In a tractor crane, the combination with a tractor having traction units at opposite sides and hoisting mechanism, of a mast mounted; on one of the traction units, a member in articulated connection with the other traction unit and with the mast for bracing the latter, a boom 111 5111):-

ported relation to the first named traction unit ing mechanism and boom arranged to support a load, a boom topping line running between the boom, the mast and the hoisting mechanism for swinging the boom, and articulated struts having cable-guiding means between the hoisting mechanism and mast arranged to absorb the stresses of said lines and to accommodate the movements of the crane structure relative to the tractor body due to independent movements of the traction units in passing over uneven ground.

10. In a tractor crane, the combination with 'a tractor having traction units at opposite sides and hoisting mechanism, of a'mast mounted on one of the traction units, a member in articulated connection with the other traction unit and with the mast for bracing the latter, a boom pivoted to the first named traction unit to swing about an axis extending lengthwise of the traction unit, a load line running between the hoisting mechanism and boom arranged to support a load, a boom topping line running between the boom, the mast and the hoisting mechanism for swinging the boom, and articulated guide means between the hoisting mechanism and mast arranged to absorb the stresses in the lines and to accommodate the movements of the crane structure relative to the tractor body due to independent movements of the traction units in passing over uneven ground, said guide means including pulleys mounted on the mast around which the load line and topping line, respectively, pass, a rigid fair lead member flexibly coupled to the mast and extending rearwardly therefrom, a post pivoted to the structure adjacent to the hoisting mechanism extending upwardly from its pivots and pivoted to the fair lead member by a knuckle joint, and guide sheaves for the respective lines mounted at said knuckle joint.

11. The combination with a tractor having traction units at opposite sides and hoisting mechanism, of a mast mounted on one of the traction units exclusively, a boom pivoted to the same traction unit to swing about an axis extending lengthwise of the unit, a mast bracing member connected to the other traction unit and to the mast and to, no other part of the tractor, and

, cables running from the hoisting mechanism to the mast and boom for raising and lowering the latter and to a load support suspended from the boom, respectively.

12. The combination with a tractor having traction units at opposite sides and hoisting mechathe mast and connected to no other part of the tractor for bracing the latter, a boom pivoted to the mast to swing to positions making difierent angles with the vertical, a load line running between the hoisting mechanism and boom arranged to support a. load, and a topping line running between the boom, the mast, and the hoisting mechanism for swinging the boom.

13. A tractor crane comprising the combination with a tractor having traction units at opposite sides, of a mast mounted at its foot end on one of the traction units-exclusively and formed with a bend so disposed that'its upper part extends transversely over the tractor, a member connected 'to the head of the mast and to the opposite traction unit exclusively at points in substantially vertical alinement for bracing the mast, a boom supported by the same traction unit on which the foot end of the mast is mounted, in pivotal relation to the mast so as to swing in her connected to the head of the mast and to the opposite traction unit exclusively at points in substantially vertical alinement for bracing the mast, a boom supported by the same traction unit on which the foot end of the mast is mounted, in pivotal relation to the mast so as to swing in a plane transverse to the length of the tractor, means between the mast and boom for swinging the boom u and down about its pivotal support. and resilient stop means carried by the mast in position to be engaged and put under strain by the boom when the latter is raised, whereby to impart force tending to lower the boom.

15. A tractor crane comprising the combination with a tractor having traction units at opposite sides, of a mast mounted at its foot end on one of the traction units exclusively and formed with a bend so disposed that its upper part extends transversely over the tractor, a member connected to the head of the mast and to the opposite traction unit exclusively at points in substantially vertical alinement for bracing the mast, a boom supported by the same traction unit on which the foot end of the mast is mounted, in pivotal relation to the mast so as toswing in a plane transverse to the length of the tractor, hoisting means for raising the boom about its pivotal support, and means for causing displacement of the boom outward from an upright position when the force of the hoisting means is relaxed.

16. A tractor crane comprising the combination with a tractor having traction units at opposite sides, of a mast mounted at its foot end on one of the traction units exclusively and formed with a bend so disposed that its upper part ex tends transversely over the tractor, a member connected to the head of the mast and to the opposite traction unit exclusively at points in substantially vertical alinement for bracing the mast, a boom supported by the same traction uniton which the foot end of the mast is mounted, in pivotal relation to the mast so as to swing in a plane transverse to the length of the tractor, hoisting means mounted on the tractor at a location displaced in the length dimension of the tractor from said transverse plane, cables running between the hoisting means and the mast disposed for controlling the boom and a load suspended therefrom, and rigid strut means between the hoisting means and mast arranged to absorb and neutralize stresses due to tension in the cables.

17. A tractor crane comprising the combination with a tractor having traction units at opposite sides and a hoisting mechanism at one end, of a mast supported at its foot end exclusively by one of the traction units, a bracing member supported exclusively by the other traction unit and connected with the head of the mast for bracing the latter, a boom supported by the same traction unit which supports the mast, in pivotal relation line running from said hoisting means to guided 12 means and the mast along the length of the strut means, said cables being arranged to control raising and lowering of the boom and of a load suspended from the boom.

18. A crane structure comprising a mast, a boom pivotally mounted for swinging movement relatively to the mast, a rigid bridle pivoted to the boom, a topping line passing between the mast head and bridle, and a spring interposed between the boom and bridle for supporting the weight of the bridle when the topping line is slack.

19; A crane structurecomprising a mast, a boom pivotally mounted for swinging movement toward and away from the mast, a bridle connected to the boom, a pulley block connected with the bridle at a point distant from the boom, pulleys on the mast, a topping line passing around said pulleys and the pulleys of said block, and a yieldable resistor disposed to react with the bridle and block to resist bobbing of the block when the tension of the topping line is altered.

20. A tractor crane comprising the combination with a tractor having traction units at opposite sides, of a mast and boom supported exclusively by one of said units, a connector between the head of the mast and the traction unit at the other side of the tractor, a stay connected between the mast and boom holding the boom inclined, hoisting means on the tractor, and a load engagement with the mast and boom for supporting loads and operable by the hoisting means to raise and lower such loads.

21. A tractor crane comprising the combination with a tractor, of a crane including a mast and boom supported entirely by the traction units of the tractor, the boom being pivotally mounted in cooperative relation to the mast at a point lower than the mast head so as to swing toward and away from the mast head, a power control unit mounted on the tractor having cable take up means, cables running between the power control unit, the mast and the boom, a strut pivotally connected at one end to the mast, a second strut pivotally mounted near said take up means, the struts being connected pivotally to 1 each other at one'side of the straight line from said unit to the connection of the first strut with the mast, and cable guiding means arranged to lead the cables along the struts.

22. A crane structure comprising a mast, a boom pivoted to swing toward and away from the mast about an axis adjacent to the foot of the mast, hoisting means at one side of the mast, a topping line and a load line leading from said hoisting means to the mast at a location between the head and foot ends thereof, and means on the most disposed to guide said lines in relatively opposite directions from the before named location; the topping line being operatively connected with the head p t o s of t e t and boom for controlling the swinging movements of to the mast so as to swing in a plane transverse the latter, and the boom having guide means over which the load line passes for supporting a load.

23. A crane structure comprising a mast, a boom pivoted to swing toward and away from the mast about an axis adjacent to the foot of the mast, cable guiding means connected with the mast at a location between the head thereof and the boom, a cable guide on the mast nearer to the boom than said cable guiding means, a pulley on the head portion of the mast, hoisting means at one side or the mast, and two cables leading from said hoisting means to said cable guiding means; one of said cables leading thence to and around said mast head pulley to operative connection with the boom for controlling the swinging movement of the boom, and the other cable passing in the relatively opposite direction to and around said cable guide and over guide means on the boom for supporting a load.

24. A crane structure comprising a mast, a boom pivoted to swing toward and away from the mast about an axis adjacent to the foot of the mast, hoisting means at one side of the mast and of the plane in which the boom is adapted to swing, a topping line and a load line leading from said hoisting means to the mast at a location between the head and foot ends thereof, strut means between the hoisting means and mast arranged to absorb and neutralize stresses due to tension in said lines, and means on the mast disposed to guide said lines in relatively opposite directions from the before named location; the topping line being operatively connected with the head portions of the mast and boom for controlling the swinging movements of the latter, and the load line passing over guide mean-s on the boom for supporting a load.

25. A crane comprising a mast having a foot end adapted for mounting on supporting means, a counter arm or tie. member adapted to be mounted at its lower end on supporting means at a distance from the foot end ofthe mast and connected at its upper end with an elevated portion of the mast, the mast being so disposed that the counter arm or tie member is substantially vertical when the mast and counter arm are operatively mounted on supporting means, a boom having a foot end adapted to be mounted adjacent to the foot end of the mast with a pivotal connection enabling it to swing in the common plane of the mast and counter arm, and tension means operatively connected with the mast and boom at points distant from the axis of the swinging movement for swinging said boom toward and away from the mast. i

26. A crane comprising the combination of a -mast and a boom adapted to be supported exclusively by one of the traction units of a tread tractor with the boom pivoted to swing laterally with respect; to the tractor, an upright member having its upper end connected to the head end portion of said mast and its lower end adapted to be mounted on a traction unit at the opposite side of the tractor, hoisting means adapted to be mounted on the tractor, and operative tension means leading from said hoisting means to the mast and boom for raising and lowering loads andior swinging the boom.

27. A crane comprising a mast having feet at its lower end spaced apart from one another and adapted to be mounted on one of the traction units of a tread tractor with its feet in a line extending lengthwise of such unit and having a head end, a counter arm or tie member connected at one end to the head end of said mast and extending downwardly therefrom, adapted to be connected at its lower end with a traction unit at the opposite side of the tractor, said counter arm being so related to the mast as to occupy a subsantially vertical position when the foot ends of the mast and counter arm are mounted on traction units at opposite sides of a tractor, a boom having a foot end adapted to be mounted adjacent to the foot end of the mast with a pivotal arrangement enabling it to swing in the common plane of the mast and counter arm, and tension means operatively interconnected between the head portions of mast and boom for so swinging the boom.

28. A tractor crane comprising the combination with a tractor having a body and traction units in pivotal connection with said body at opposite sides thereof to swing about a horizontal axis, of a mast and boom supported exclusively by one of said traction units, a member supported exclusively on the other traction unit and connected to the mast for bracing it, the boom being pivoted to swing about an axis extending longitudinally of the tractor, means for applying force between the mast and boom for swingin the boom, and means on the boom by which a load may be supported.

ROBERT CASPER SWANEY.

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